Shoichi Kusanagi - He's hacker like Yusaku and hacker rivals.

Naoki Shima - Probably is trying to be Yusaku's friend, but he's mean... (My predictions)

Akira Zaizen - Probably Aoi's brother...

Ema Bessho - No idea... Maybe Yusaku's fan girl xD

The first episode is named: My name is Playmaker

VRAINS means Virtual Reality Artificial Intelligence and Network System

Well, for now we'll wait the first episode ^^